Cyanine dyes



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9 Claims. 1, asg znas).

This invention relates to cyanine dyes which are of value as sensitisers for photographic; silver halide emulsimm According to the present invention there is provided a new class of cyanine dye bases of the general Formula I:

R CO CORn in Wit??? 5; 2. and re lkyl roup and Kris se ec ed from the class consisting of alkyl and alkoxy groups, R; M 3 tssethsr ummin e h 12 ar a atoms, and'wherein'the benzene rings may, contain one or. W? halogen, alkyl, alkoxy or aryl groups. The said dyestuffs, and particularly those in which R1, R2 and R3 are lower alkyl groups. containing up to'4 carbon atoms, and R4 is methyl, ethyl and methoxy', groups, are valuable sensitisers for photographidsilver halide emulsions, imparting to silver iodobromide emulsions, for example, a strong sensitivity in'the green and red regions of "the spectrum. The present invention includes photographic silver halide emulsions containing the aforesaid dyestuffs in sensitising amdunt. I

Accord'ng to a further feature of the present invention, the said cvanine dyes are prepared by reacting a cyanine dye salt of the Formula II:

R20 0 0 OR;

III

where Rs'is an alkyl, aralkyl or aryl group, the other symbols have the meaningsassigned to them above and the benzene rings maybesubstituted as indicated above, with a B-diearbonyl compound of the formula R2COCHaCOR4 where R and R4 have the meanings assigned to them above.

Referring to, the symbols used in the foregoing formulaeQit is to be understood'that'where alkyl groups arereferred'to these rnay be, 'for example, methyhethyl, p rppy'l, but yl or a higher alkyl group, and where aryl groupsare referred to these may be, for example, phenyl orfnaphth'yl. 'Alkoxy groups may be derived from any of the foregoing allryl groups. Halogensubsjtituents on the benzene rings may, be, for example, chlorine or bromine atoms.

It is an essential characteristic of the present invention that the reaction shall be carried out with the aid of a strongbasei Itis preferreduo use'a strong inorganic base such as an alkali metal hydroxide, e. g. sodium or potassium hydroxide, but strong quaternary ammonium bases may, also be employed, e. g." trimethyl benzyl am moniuin hydroxide. Alkali metal alkoxides may also be employed'and similar strong bases such as sodamide. Strong "organic bases may also be employed, but are generally less efiicient. Preferably the'reaction is effected in a medium of pyridine.

The following examples will serve to illustrate the invention, but are not to be regarded'as limiting it in any way:

EXAMPLE 1 l repar rtio n of 2 :3-diethyl:9-(acetylcarbethoxymethyl)- tl iincarbocyanine 0.64 gm. 3:3-diethyl-9-(acetylcarbethoxymethyl) thiacarbocyanine iodide was mixedwith 5 'mlsfof pyridine and 1 ml. of 40% w./v. aqueous sodium hydroxide. The mixture was heated on a steam bath with frequent shaking 0530 40 minutes and'then poured into ml. of dry ether to precipitate the dye." The dye was filtered 011 and washqdwith mo t r an w ter- 'Ihe crude dye was crystallised from 50 mls. acetone to-give purplecrystals with M. Pt. 204-206 C. (d).

Anqlysis.S. Req. 13.01%, found 12.93%. V This dye when incorporated in a silver iodobromide emulsion extends the sensitivity to 6400 A. with maxima at 5409 A., 5800 A. and 6100- A.

EXAMPLE 2 Method (a).-0.48 gm. 3:3'-dimethy1-9-(diacetylmethyl) thiacarbo'cyanine bromide, 10 mls. ethanol and 0.6 ml. of a 40% w./v. solution of benzyltrimethyl ammonium hydroxide were mixed and heated under reflux for /2 hour. The alcohol'wa's then removed under reduced pressure and the residue stirred with ether and filtered." After washing with water and drying, the crude dye was purified by'solution in 25 mls. ethanol, evapor'atin'gto' 10 'mls." and leaving to cool and crystallise. The dye separated as purple crystals with a bronze'refiex, MIP t.'228'C."(d).'* Arialysisr-N Req. 6.45%, 14;55%", found 13L97%.

This dye, when incorporated in a silver iodobromide emulsion, extends the sensitivity to 6450 A. with maxima at 570 0 A. and 5250 A.

Zkiethod (b).0.25 gm. 3:3-dimethyl-9-(diacetylmethyl) thiacarbocyanine bromide and 0.02 gm. of sodium in 3 mls. of ethanol were mixed and heated under reflux for /2 hour. The alcohol was removed under reduced pressure and the residue stirred with ether, filter'e'd'and washe'cl'with water'l" The dye obtained'had'M.'Pt. 228C. (d).

Method (c).--0.40 3:3'-dimet hyl-9,-(diacetylfound 6.14%; S Req.

methyl) thiacarbocyanine bromide, mls. ethanol and 0.48 ml. aqueous sodium hydroxide solution were mixed and heated under reflux for /2 hour. The alcohol was then evaporated under reduced pressure and the residue stirred with ether and filtered. The dye after washing with water had M. Pt. 222 C. (d).

Method (d).0.48 gm. 3:3 dimethyl 9 (diacetylmethyl) thiacarbocyanine bromide and 5 mls. pyridine were mixed and heated on the water bath until most of the dye was in solution, when a solution of 0.035 gm. of sodium hydroxide in 0.8 ml. water was added. After heating for 10 minutes the mixture was cooled, diluted with 60 ml. of ether and water. The crude dye was recrystallised from ethyl alcohol. M. Pt. 230-231 C. (d).

EXAMPLE 3 Preparation of 3:3-diethyl-9(acetylcarbomethoxymethyl) thiacarbocyanine 0.49 gm. 3:3-diethyl-9-(acetylcarbomethoxymethyl) thiacarbocyanine iodide was mixed with 5 mls. of pyridine and a solution of 0.04 gm. sodium hydroxide on 0.5 ml. water, and the mixture heated on a steam bath for 8 minutes. It was then cooled, diluted with ether (100 mls.), filtered and the residue washed with water. The crude dye was taken up in 40 mls. of ethanol from which starting material separated after concentration to 10 mls. This was filtered off and from the filtrate the product was precipitated as purple needles (M. Pt. 241- 243 C. (d)) by the addition of dry ether.

Analysis.-N. Req. 5.84%, found 5.78%.

When incorporated in a silver iodobromide emulsion the sensitivity was extended to 6350 A. with a broad maximum at about 6000 A.

EXAMPLE 4 Preparation of 3:3'-diethyl-9-diacetylmethyl thiacarbocyanine 1.0 gm. 3:3-diethyl-9-diacetylmethyl thiacarbocyanine iodide was mixed with 5 mls. of pyridine and a solution of 0.08 gm. sodium hydroxide in 0.8 ml. water. The mixture was heated for 12 minutes on the steam bath and then cooled, diluted with 130 mls. of ether and filtered. After washing with water and drying the crude dye was twice purified by solution in ethanol followed by fractional precipitation with ether. The first fraction in each case contained traces of starting material. The

purified product separated as green needles, M. Pt.

Analysis.-N. Req. 6.05%, found 5.90%.

This dye, when incorporated in a silver iodobromide emulsion, extends the sensitivity to 6400 A. with a maximum at 6200 A.

EXAMPLE 5 Preparation of 3:3'-dimethyl-5-chloro-9-diacetylmethyl thiacarbocyanine 0.67 gm. of 3:3'-dimethyl-5-chloro-9-diacetylmethyl thiacarbocyanine iodide was mixed with 5 mls. of pyridine and 1.12 mls. of w./v. aqueous potassium hydroxide and heated with frequent shaking on a steam bath for 20 minutes. The mixture was then diluted with 100 mls. of ether, filtered and washed with water. The crude dye was purified by fraction precipitation from ethanol by the addition of ether and separated as purple crystals.

This dye, when incorporated in a silver iodobromide emulsion, extends the sensitivity to 6500 A. with a maximum at 6150 A.

EXAMPLE 6 Preparation of 3:3-diethyl-5 :5 -dimethyl-9-(diacetylmethyl) thiacarbocyanine 0.90 gm. 3 :3-diethyl-5 5 '-dimethyl-9-(diacetylmethyl) thiacarbocyanine iodide was mixed with 5 mls. of pyridine and 0.56 ml. 50% w./v. aqueous potassium hydroxide and then heated on the steam bath for hour. The mixture was then cooled, diluted with ether, filtered and the residue washed with water. The crude dye was dissolved in 10 mls. of ethanol, from which a little starting material crystallised on cooling. After this was filtered oil, dry ether was added to the filtrate to precipitate the product as dark green crystals, M. Pt. 2l2-213 C. (d).

This dye, when incorporated in a silver iodobromide emulsion, extends the sensitivity to 6250A. with a maximum at 5900 A.

What we claim is:

1. A cyanine dye base selected from the class consisting of dye bases of the general formula:

R 00 COR:

CHaCO COOCzHr (3=CH i CH=C O t I 0.11. 6

3. The compound 3:3'-dimethyl-9-(diacetylmethyl) thiacarbocyanine of the formula:

CHaCO COCH:

(f .=..iti..=. in. .511.

4. The compound 3 3-diethyl-9-(acetylcarbomethoxymethyl) thiacarbocyanine of the formula:

CHaO O O O O CH;

5. The compound 3:3-diethyl-9-diacetylmethyl thiacarbocyanine of the formula:

CHaCO COOH;

i C 2H5 6. The compound 3:3'-dimethy1-5-ch1oro-9-diacetylmethyl thiacarbocyanine of the formula:

011,0 0 0 CH3 S o C=CH-il )-0H=C in, L,

7. A process for the production of a cyanine dye base selected from the class consisting of dye bases of the general formula:

COR: S

with a strong base.

8. A process for the production of a cyanine dye base selected from the class consisting of dye bases of the general formula:

COR:

where R1, R2 and R3 are alkyl groups containing up to 4 carbon atoms, R; is selected from the class consisting of alkyl and alkoxy groups containing up to 4 carbon atoms, and corresponding compounds in which the benzene rings carry from one to two substituents selected from the group consisting of alkyl and alkoxy groups containing up to 4 carbon atoms, phenyl, chlorine and bromine substituents, which process comprises reacting a compound of the general formula:

with an alkali metal hydroxide.

9. A process for the production of a cyanine dye base selected from the class consisting of dye bases of the general formula:

RCO COR:

where R1, R2 and R3 are alkyl groups containing up to 4 carbon atoms, R; is selected from the class consisting of alkyl and alkoxy groups containing up to 4 carbon atoms, and corresponding compounds in which the benzene rings carry from one to two substituents selected from the group consisting of alkyl and alkoxy groups containing up to 4 carbon atoms, phenyl, chlorine and bromine substituents, which process comprises reacting a compound of the general formula:

R16 0 00R4 S CH C=CH(J=CHC l R1 R: X

with an alkali metal hydroxide in a medium of pyridine.

No references cited. 

1. A CYANINE DYE BASE SELECTED FROM THE CLASS CONSISTING OF DYE BASES OF THE GENERAL FORMULA: 